A known hydraulic accumulator includes a housing, a cover, a piston and a spring (see, for example, JP2016-169768A).
The housing includes a tubular portion, which opens at one axial end side. The cover closes the tubular portion at the one axial end side. The piston is received in an inside of the tubular portion in a manner that enables movement of the piston in an axial direction. The piston forms an oil pressure chamber, which accumulates the oil pressure, at the other axial end side, which is opposite from the one axial end side. The spring is interposed between the cover and the piston to urge the piston toward the other axial end side.
In this hydraulic accumulator, the cover is urged by the spring toward the one axial end side. Therefore, it is necessary to limit removal (detachment) of the cover from the tubular portion. In view of the above point, there is also known a structure that holds the cover, which is urged by the spring, through use of a snap ring by fitting the snap ring in a circumferential groove that is formed in an inner peripheral wall of the tubular portion.
The removal limiting structure, which limits the removal of the component through use of the snap ring, is also known in other technical fields, which is other than the technical field of the hydraulic accumulator discussed above.
For example, in a case of a starter that starts an internal combustion engine, there is a known structure that holds a load, which is exerted from an armature to a motor output shaft (armature shaft) in a thrust direction, through use of a snap ring that is installed to an outer peripheral wall of the motor output shaft (see, for example, JP4645389B2). Furthermore, in a case of a ball bearing installed to a vehicle, there is a known structure that holds a load, which is exerted from an outer race member of the ball bearing in a thrust direction, through use of a snap ring that is installed to an inner peripheral wall of a vehicle side component, to which the outer race member of the ball bearing is press fitted (see, for example, JP2005-207571A).
In general, in the structure, which limits the removal (detachment) of the component through use of the snap ring, it is necessary to limit removal of the snap ring from the corresponding groove since the snap ring limits the removal of the component through the fitting of the snap ring in the groove. With respect to this point, in the removal limiting structure of JP2016-169768A, the groove is formed at the outer peripheral wall of the cover, and the snap ring is fitted into this groove to limit removal of the snap ring from the groove. Furthermore, in the removal limiting structure of JP4645389B2, an element, which circumferentially clamps two end portions of the snap ring that forms a ring end gap therebetween, is installed to limit an increase in a diameter of the snap ring and thereby to limit removal of the snap ring from the groove.
However, in the case of the removal limiting structure of JP2016-169768A, in order to fit the inner peripheral portion and the outer peripheral portion of the snap ring into the groove of the tubular portion and the groove of the cover, respectively, a complicated assembling work may be required, so that implementation of the removal limiting structure of JP2016-169768A is difficult. Furthermore, the removal limiting structure of JP4645389B2 limits the increase in the diameter of the snap ring. In contrast, in the hydraulic accumulator, the snap ring is installed to the inner peripheral wall of the tubular portion. Therefore, in the case of the hydraulic accumulator, there is no possibility of increasing of the diameter of the snap ring. Rather, there is a possibility of removal of the snap ring through a decrease in the diameter of the snap ring. Therefore, even if the removal limiting structure of JP4645389B2 is used in the hydraulic accumulator, it is impossible to limit removal of the snap ring from the groove.